1. Field
The present disclosure relates generally to sound attenuation and, in particular, to sound attenuation using a cellular core. Still more particularly, the present disclosure relates to a method and apparatus for attenuating sound using cell interface channels between cells of a cellular core.
2. Background
Sound attenuation is the combined effect of scattering and absorption that, together, control sound. Scattering is the reflection of sound in directions other than the original direction of propagation of the sound. Absorption is the conversion of sound energy into other forms of energy. Different types of structures may be used to attenuate sound.
A structure that includes a honeycomb core sandwiched by a porous face sheet on one side and an impervious face sheet on the other side is an example of one type of structure that may be used to attenuate sound. A honeycomb core may take the form of, for example, without limitation, a cellular core that has the geometry of a honeycomb. Honeycomb cores may be used in different applications. As one example, honeycomb cores are oftentimes attached to the inner walls of the inlet ducts inside aircraft engine systems to attenuate the sound generated by these engine systems. However, some currently available honeycomb cores may be unable to provide the levels of sound attenuation desired without increasing the cost and weight of the aircraft more than desired.
For example, some currently available types of honeycomb cores use septa located within the cells of the honeycomb core to enhance sound attenuation. A septum may be an insert that is inserted into or formed internally within a cell. The septum may divide the single cell along the length of the cell. Although these type of septa may help with sound attenuation, fabricating these internal septa within the cells of the honeycomb core may be more laborious and technologically challenging than desired.
Further, the type and amount of material used to make these septa may make adding these septa to honeycomb cores more expensive than desired. In some cases, the cost associated with these septa may be more expensive than desired. For example, honeycomb cores having these internal septa may be four to five times more expensive than honeycomb cores with no internal septa.
Additionally, internal septa within the cells of a honeycomb core may increase the weight of the honeycomb core more than desired. This added weight may increase the weight of the platform within which the honeycomb core is installed more than desired. Therefore, it would be desirable to have a method and apparatus that take into account at least some of the issues discussed above, as well as other possible issues.